Tube pumps required to be rotated in the normal and reverse directions are publicly known. In such a conventional tube pump, the rotor is rotated forcibly in the reverse direction without changing the mechanism thereof, because of the running time is short or the like. Several pumps of this same kind, but different in rotary direction from one another are also known.
One commercially available tube pump is disclosed in the patent materials, for example, Japanese Patent Application Laid-Open No. 218042/1994.
FIG. 4 to FIG. 6 show other conventional tube pumps, wherein reference numeral 1 denotes a housing (exterior) for mounting a resilient tube (not shown), at an inner peripheral surface of the housing, 2 denotes a rotor element maintaining a roller to be pressed to the resilient tube, 3 denotes a motor for driving the rotor element 2, 4 denotes three arm-shaped swing portions, each base end of which being supported rotatably through a shaft 5 by the rotor element 2 at each of positions equidistantly apart from one another by 120° on a circle, and each free end of which being extended in a direction different by 135°, for example, from the radial direction of the rotor element 2, 6 denotes rollers, each mounted rotatably on a free end of each swing portion 4, and 7 denotes buffer members, each inserted between the rotor element 2 and a substantial intermediate portion of the corresponding swing portion 4.
As shown in FIG. 7, each of the buffer members 7 comprises a rod 11 having a collar 8 fixed to one end thereof so as to engage with an engaging pin 9 projected from the rotor element 2, and having an elongated hole 10 formed on the other end thereof, a connecting pin 12 projected from the corresponding swing portion 4 and inserted into the corresponding elongated hole 10, and a spring 13, one end of which being contacted to the collar 8 fixed to the rod 11, and the other end of which being contacted to a substantial intermediate portion of the corresponding swing portion 4.
In the conventional tube pump, the resilient tube is pressed by the roller 6 which is positioned on the free end of the swing portion 4 and urged outwardly in the radial direction of the roller element 2 by the buffer member 7 when the rotor element 2 is rotated in the normal direction (counter-clockwise direction) 14 as shown in FIG. 6, so that the resilient tube is squeezed and liquid is sucked into the tube and exhausted from the tube.
In this case, a load 15 having pulsations specific to the tube pump in a direction across the normal direction 14 is applied to the roller 6, however, such load 15 is reduced by the spring action of the spring 13 of the buffer member 7.